KR20220121860A - Method for determining line angle and rotation of multiple patterning - Google Patents

Abstract

Methods and apparatus for determining line angles and line angle rotations of gratings or line features are disclosed. One aspect of the disclosure includes measuring coordinate points of a first line feature using a measurement tool, determining a first slope of the first line feature from the coordinate points, and from the slope of the first line feature It involves determining the first line angle. This process may be repeated to find a second slope of the second line feature near the first line feature. The slope of the first and second line features may be compared to find the line angle rotation. Line angle rotation is compared to design specifications and stitch quality is determined.

Description

Method for determining line angle and rotation of multiple patterning

[0001] Embodiments of the present disclosure generally relate to apparatus and methods for optical device fabrication. More specifically, embodiments of the present disclosure relate to apparatus and methods for measuring the stitch quality of a grating structure integrated into a waveguide.

[0002] Virtual reality is generally considered to be a computer generated simulated environment, in which the user has an apparent physical presence. The virtual reality experience is created in three dimensions (3D), and a near-eye display panel as a head-mounted display (HMD), such as glasses, or lenses for displaying a virtual reality environment replacing the real environment. can be viewed with other wearable display devices having

[0003] However, augmented reality allows a user to still see through the display lenses of glasses or other HMD device to view the surrounding environment, but also see images of virtual objects created for display and appearing as part of the environment. make the experience possible. Augmented reality may include any type of input, such as audio and haptic inputs, as well as video, graphics, and virtual images that enhance or augment the environment the user experiences. As an emerging technology, augmented reality has many challenges and design constraints.

[0004] One such challenge is to display a virtual image overlaid on the surrounding environment. Waveguides are used to assist in overlaying the images. The generated light propagates through the waveguide until it exits the waveguide and is overlaid on the surrounding environment. Fabricating waveguides can be tricky because waveguides tend to have non-uniform properties. A common problem when creating waveguides is the ability to measure the stitch quality of grating lines. Previous attempts to measure stitch quality have proven expensive and time consuming. Accordingly, there is a need in the art for improved methods and systems for quantifying the stitch quality of grating lines on a grating structure.

[0005] In one embodiment, a method of measuring a line angle is provided. The method includes selecting a field of view of the grid structure, identifying a line feature using a measurement tool, and selecting a starting point along the line feature. A primary coordinate is measured, the primary coordinate comprising a first x-coordinate and a first y-coordinate, the first x-coordinate being a first distance from the edge of the field of view to the primary coordinate. A quadratic coordinate is measured along the line feature, the quadratic coordinate comprising a second x-coordinate and a second y-coordinate, the second x-coordinate being a second distance from the edge of the field of view to the second coordinate. A theoretical line feature is estimated using the primary and secondary coordinates, and a line angle measurement between the theoretical line feature and the reference axis is calculated.

[0006] In another embodiment, a method for measuring line angular rotation of a grating structure is provided. The method includes measuring a first line angle. Measuring the first line angle includes selecting a field of view of the grating structure, identifying a line feature using a measurement tool, and selecting a starting point along the line feature. A primary coordinate is measured, the primary coordinate comprising a first x-coordinate and a first y-coordinate, the first x-coordinate being a first distance from the edge of the field of view to the primary coordinate. A quadratic coordinate is measured along the line feature, the quadratic coordinate comprising a second x-coordinate and a second y-coordinate, the second x-coordinate being a second distance from the edge of the field of view to the second coordinate. A theoretical line feature is estimated using the primary and secondary coordinates, and a line angle measure between the theoretical line feature and the reference axis is calculated. The second line angle is measured using the same method used to measure the first line angle. The difference between the first line angle and the second line angle is calculated to determine the line angle rotation, and the line angle rotation is compared to a design specification line angle measurement.

[0007] In yet another embodiment, a method for measuring line angular rotation of a grating structure is provided. The method includes positioning a measurement tool to measure a first image exposure in the grating structure. The method further includes measuring the first line angle. Measuring the first line angle includes selecting a field of view of the grating structure, identifying a line feature using a measurement tool, and selecting a starting point along the line feature. A primary coordinate is measured, the primary coordinate comprising a first x-coordinate and a first y-coordinate, the first x-coordinate being a first distance from the edge of the field of view to the primary coordinate. A quadratic coordinate is measured along the line feature, the quadratic coordinate comprising a second x-coordinate and a second y-coordinate, the second x-coordinate being a second distance from the edge of the field of view to the second coordinate. A theoretical line feature is estimated using the primary and secondary coordinates, and a line angle measure between the theoretical line feature and the reference axis is calculated. A measurement tool is positioned to measure the second image exposure in the grating structure. The second line angle is measured using the same method used to measure the first line angle. The difference between the first line angle and the second line angle is calculated to determine the line angle rotation, and the line angle rotation is compared to a design specification line angle measurement. The stitch quality is determined from the difference between the first line angle and the second line angle.

[0008] In such a way that the above-listed features of the present disclosure may be understood in detail, a more specific description of the present disclosure, briefly summarized above, may be made with reference to embodiments, some of which are appended It is illustrated in the drawings. It should be noted, however, that the appended drawings illustrate exemplary embodiments only and should not be considered limiting of their scope, but may admit to other equally effective embodiments.
1 illustrates a top view of a waveguide coupler according to an embodiment of the present disclosure;
2 illustrates a schematic top view of a plurality of gratings formed by two adjacent image exposures, according to an embodiment of the present disclosure;
3 illustrates a schematic top view of a grating and measurement features of the grating according to an embodiment of the present disclosure;
4 illustrates a schematic diagram of an interface boundary between two adjacent line features, according to an embodiment of the present disclosure;
5 illustrates operations of a method for determining a line angle of a grating line, according to an embodiment of the present disclosure.
6 illustrates operations of a method for determining a stitch process quality of a grating structure, according to an embodiment of the present disclosure.
To facilitate understanding, like reference numbers have been used where possible to designate like elements that are common to the drawings. It is contemplated that elements and features of one embodiment may be beneficially incorporated into other embodiments without further recitation.

[0016] Aspects of the present disclosure relate to apparatus and methods for determining line angle and stitch quality of grating structures. In one example, the line angle is determined by measuring discrete coordinates along the line feature. In another example, the line rotation angle is determined by measuring the line angles of multiple adjacent line grating sections.

[0017] 1 illustrates a top view of a waveguide coupler 100 according to an embodiment of the present disclosure. The waveguide coupler 100 described below is an exemplary waveguide coupler, and it should be understood that other waveguide couplers having different designs may benefit from the embodiments described herein. The waveguide coupler 100 includes an input coupling region 102 defined by a plurality of gratings 108 , an intermediate region 104 defined by a plurality of gratings 110 , and a plurality of gratings 112 . an output coupling region 106 defined by The grating section 120 of the plurality of gratings 112 is within the output coupling region 106 . The grating section 120 comprises a small section of the overall output coupling region 106 , which is described in more detail below. The input coupling region 102 receives incident beams of light (virtual image) having a constant intensity from the microdisplay.

[0018] Each grating, such as a fin structure, of the plurality of gratings 108 splits the incident beams into a plurality of modes, each beam having a mode. Zero-order mode (T0) beams are reflected back or transmitted through waveguide coupler 100, and positive first-order mode (T1) beams couple through waveguide coupler 100 to intermediate region 104 and the negative primary mode (T-1) beams propagate in the opposite direction to the T1 beams in the waveguide coupler 100 . Ideally, the incident beams are split into T1 beams with all intensities of the incident beams to direct the virtual image to the intermediate region 104 . One approach to splitting an incident beam into T1 beams having all intensities of the incident beams is to use fins comprising gratings 108, with a slant angle to suppress T-1 beams and T0 beams. it will be used The T1 beams undergo total-internal-reflection (TIR) through the waveguide coupler 100 until the T1 beams contact the plurality of gratings 110 in the intermediate region 104 . A portion of the input coupling region 102 may have gratings 108 having an angle of inclination that is different from the angle of inclination of the gratings 108 from an adjacent portion of the input coupling region 102 .

[0019] The T1 beams contact the fins of the plurality of gratings 110 . T1 beams are T0 beams that are reflected back or transmitted through waveguide combiner 100 , T1 beams that undergo TIR in the intermediate region 104 until the T1 beams contact another fin of the plurality of gratings 110 , and T-1 beams coupled to an output coupling region 106 via a waveguide coupler 100 . The T1 beams that undergo TIR in the intermediate region 104 may pass through the intermediate region 104 or until the intensity of the T1 beams coupled to the intermediate region 104 via the waveguide coupler 100 is greatly depleted. The remaining T1 beams propagating continue to contact the gratings of the plurality of gratings 110 until they reach the end of the intermediate region 104 .

[0020] The plurality of grids 110 adjusts the field of view of the virtual image generated from the microdisplay from the user's point of view to increase the viewing angle at which the user can view the virtual image, the output coupling area 106 ) is tuned to control the T1 beams coupled to the intermediate region 104 via the waveguide combiner 100 to control the intensity of the T-1 beams coupled to . One approach for controlling the T1 beams coupled to the intermediate region 104 via the waveguide coupler 100 is to control the intensity of the T-1 beams coupled to the output coupling region 106 with a plurality of gratings. It is to produce the angle of inclination of each pin of the 110. A portion of the intermediate region 104 may have gratings 110 having an angle of inclination that is different from the angle of inclination of the gratings 110 from an adjacent portion of the intermediate region 104 . Moreover, the gratings 110 may have fins having angles of inclination that are different from the angles of inclination of the fins of the gratings 108 .

[0021] The T-1 beams coupled to the output coupling region 106 via the waveguide coupler 100 are TIR in the waveguide coupler 100 until the T-1 beams contact the grating of the plurality of gratings 112 . where T-1 beams are split into T0 beams that are either reflected back or transmitted through waveguide coupler 100 . The T1 beams undergo TIR in the output coupling region 106 until the T1 beams contact another pin of the plurality of gratings 112 and the T-1 beams are coupled out in the waveguide coupler 100 . The T1 beams that undergo TIR in the output coupling region 106 are irradiated until the intensity of the T1 beams coupled to the output coupling region 106 via the waveguide coupler 100 is significantly reduced or the output coupling region 106 . ) continue to contact the pins of the plurality of gratings 112 until the remaining T1 beams propagating through ) reach the end of the output coupling region 106 . The plurality of gratings 112 are arranged in the waveguide coupler 100 to further adjust the field of view of the virtual image generated from the microdisplay from the user's point of view, further increasing the viewing angle through which the user can view the virtual image. To control the intensity of the coupled out T-1 beams, it is tuned to control the T-1 beams that are coupled to the output coupling region 106 via the waveguide coupler 100 .

[0022] One approach for controlling the T-1 beams coupled to the output coupling region 106 via the waveguide coupler 100 is to use a plurality of gratings 112 to further adjust the field of view and increase the field of view. It is to produce the inclination angle of each pin. A portion of the intermediate region 104 may have gratings 110 having a fin tilt angle that is different from the inclination angle of the fins of the gratings 110 from an adjacent portion of the intermediate region 104 . Moreover, gratings 112 may have fin tilt angles different from those of gratings 108 and gratings 110 . In some embodiments, the structures of 108, 110 and 112 are 2D patterns, such as a rotated elongated pillar, a via hole feature, or a circular pillar.

[0023] 2 illustrates a schematic top view of a plurality of gratings 112 formed by two image exposures, according to an embodiment of the present disclosure. FIG. 2 is illustrated in FIG. 1 as a grating section 120 comprising a portion of the output coupling region. The grating section 120 is shown with reference to the x-coordinate, y-coordinate, and z-coordinate. The plurality of gratings 112 includes a grating structure 200 . The grating structure 200 includes a first set of line features 204 formed by a first image exposure and a second set of line features 206 formed by a second image exposure. The first set of line features 204 and the second set of line features 206 intersect at a junction 202 . The junction 202 may be considered a point at which the two sets of line features 204 , 206 are joined together during processing. The junction 202 results from the use of multiple masks or image exposures to create the grating structure 200 .

[0024] Using multiple masks to create the grating structure 200 significantly lowers mask design and fabrication costs. Although some attempts have been made to create masks large enough to create a plurality of gratings 112 that cover the entire output coupling region 106 , using a single mask has been found to be extremely expensive. Current methods of creating a plurality of gratings 112 utilize multiple masks or repeated use of the same mask to pattern the grating structure 200 . For example, the grating structure 200 is made of sections including a first section S1 and a second section S2 . The first and second sections S1 , S2 may be described as image exposures. The first section S1 includes a first set of line features 204 and the second section S2 includes a second set of line features 206 . In some embodiments, additional sections are utilized, which are stitched together with joints 202 between each section. Additional sections may be stitched together to constitute the entirety of the plurality of gratings 112 within the output coupling region 106 . The stitching process described above with respect to the plurality of gratings 112 and the output coupling region 106 is the plurality of gratings 108 and the input coupling region 102 or the plurality of gratings 110 and the intermediate region. (104) can be similarly applied.

Each of the line features 204 , 206 includes a line angle θ ₁ , θ ₂ , respectively. The first line angle θ ₁ is defined as the angle between the x-axis and the plurality of gratings 112 in the first set of line features 204 . The second line angle θ ₂ is defined as the angle between the x-axis and the plurality of gratings 112 in the second set of line features 204 . Representative line angles θ ₁ and θ ₂ are shown on the lowermost grating of section S1 and section S2, respectively. However, the line angles θ ₁ , θ ₂ are found from any one of the plurality of gratings 112 of section S1 and section S2 . In some embodiments, individual line angles θ ₁ , θ ₂ are found for each of the plurality of gratings 112 in the first and second sections S1 , S2 . Thus, line angle measurements for each grating with respect to the x-axis can be obtained. The line angle measurements in section S1 are averaged to find a first average line angle. The line angle measurements in section S2 are also averaged to find a second average line angle.

In alternative embodiments, the line angles θ ₁ , θ ₂ are calculated relative to the y-axis. Line angles can be found for any line or axis within the same plane of line angles as long as the axis is used consistently for all line angle measurements. Consistent utilization of a line or axis as a reference line serves the purpose of providing a common reference point and enabling comparison between line angle measurements.

[0027] 3 illustrates a schematic top view of a grating and measurement features of the grating according to an embodiment of the present disclosure; 3 further illustrates a field of view 300 of the measurement tool. In some embodiments, the measurement tool comprises a scanning electron microscope. The field of view 300 includes a grid structure. The grating structure may be similar to the grating structure 200 as shown in FIG. 2 . Within the field of view 300 of the measurement tool is a line feature 302 . The measurement tool can identify one or more line features 302 . The line feature 302 of FIG. 3 may be similar to any of the plurality of gratings 112 described in connection with FIGS. 1 and 2 . Although only one line feature 302 is shown in FIG. 3 , it is generally understood that multiple line features 302 will be within the field of view 300 of the measurement tool at any given time. The measurement tool is capable of distinguishing between each line feature 302 such that the measurement tool can focus on one line feature 302 when multiple line features 302 are within the field of view 300 . It is part of the tool assembly. The measurement tool assembly distinguishes between each line feature by using a line tracing program. The line trace program may be part of a controller or computer that measures data from the measurement tool. Line feature 302 discussed in connection with FIG. 3 is part of a section of line features 302 , such as line features 204 and 206 of FIG. 2 . Only one line feature 302 is shown in FIG. 3 . In other embodiments (not shown here), the line features are elongate bar shapes, circular pillars, or via hole shapes.

[0028] The line feature 302 may be measured using discrete coordinate point measurements along a central axis that travels through the length of the line feature 302 . For example, discrete coordinate point measurements include primary coordinates 320 , secondary coordinates 330 , tertiary coordinates 340 , and nth coordinates 350 . The n-th coordinate represents any coordinate in the sequence of coordinates past the cubic coordinate 340 . In some embodiments, the nth coordinate is a fourth coordinate, a fifth coordinate, a sixth coordinate, or more coordinates. There may be separate coordinate points not shown in FIG. 3 . Coordinates 320 , 330 , 340 , 350 are found at the center of the measurement areas. The primary coordinates 320 are positioned at the center of the first measurement area 304 . The secondary coordinates 330 are positioned at the center of the second measurement area 306 . The cubic coordinates 340 are positioned at the center of the third measurement area 308 . The n-th coordinate is positioned at the center of the n-th measurement area 310 . The starting point along the line feature 302 may be the primary coordinate 320 , or the intersection of the line feature 302 with the edge of the field of view 300 closest to the primary coordinate 320 . Alternatively, the starting point may be the point between the first coordinate 320 and the intersection of the line feature 302 with the edge of the field of view 300 closest to the primary coordinate 320 . The distance from the edge of the field of view 300 that intersects the line feature 302 to the primary coordinates 320 is less than about 500 nm, such as less than 400 nm, such as less than 300 nm. In some embodiments, the distance from the edge of the field of view 300 that intersects the line feature 302 to the primary coordinates 320 is between about 300 nm and about 400 nm, such as about 350 nm. In some embodiments, the distance from the edge of the field of view 300 that intersects the line feature 302 to the starting point is less than about 400 nm, such as less than about 350 nm, such as less than about 250 nm, or such as 150 nm. is less than

[0029] In some embodiments, the primary coordinate 320 , the secondary coordinate 330 , the tertiary coordinate 340 , and the n-th coordinate 350 may all be measured about the x-axis and the y-axis. The x-axis and y-axis may be any x-y reference axes selected by the user. In this embodiment, the primary coordinate 320 includes a first x-coordinate and a first y-coordinate, the first x-coordinate being the first from the edge of the field of view 300 to the primary coordinate 320 . is the street In this embodiment, the y-axis, and the zero point of the x-axis are the edge of the field of view 300 . The edge of the field of view 300 including the y-axis is an edge parallel to the line feature 302 . The y-axis can also be in the same plane on the z-axis. The y-coordinate of a primary coordinate is any y-coordinate along the y-axis.

[0030] The secondary coordinate 330 includes a second x-coordinate and a second y-coordinate, and the second x-coordinate is a second distance from the edge of the field of view 300 to the secondary coordinate 330 . The second x-coordinate and the second y-coordinate are found using the same x-axis and y-axis as were used to find the first x-coordinate and the first y-coordinate.

[0031] The cubic coordinate 340 includes a third x-coordinate and a third y-coordinate, the third x-coordinate being the third distance from the edge of the field of view 300 to the cubic coordinate 340 . The third x-coordinate and the third y-coordinate are found using the same x- and y-axes used to find the first x-coordinate and first y-coordinate.

[0032] The nth coordinate 350 includes an nth x-coordinate and an nth y-coordinate, and the nth x-coordinate is the nth distance from the edge of the field of view 300 to the nth coordinate 350 . The nth x-coordinate and the nth y-coordinate are found using the same x- and y-axes used to find the first x-coordinate and first y-coordinate.

[0033] Each of the primary, secondary, tertiary, and nth coordinates is found with respect to each other and using the same x-axis and the same y-axis. An alternative method may utilize coordinate systems other than the x-y axis, such as a radial coordinate system.

[0034] The first interval distance 312 is the distance between the first measurement area 304 and the second measurement area 306 . The second spacing distance 314 is a distance between the second measurement area 306 and the third measurement area 308 . In some embodiments, the first spacing distance 312 and the second spacing distance 314 are the same distance. Alternatively, the first spacing distance 312 and the second spacing distance 314 are different distances, such that the first spacing distance 312 is less than the second spacing distance 314 . In another embodiment, the first spacing distance 312 is greater than the second spacing distance 314 .

[0035] There may be subsequent spacing distances between each measurement area up to the nth measurement area 310 . In this embodiment, the spacing distances 312 , 314 , etc. between each measurement area may be the same distance or different distances. In some embodiments, the distances between each measurement area alternate between a first spacing distance 312 and a second spacing distance 314 . In some embodiments, the spacing distances 312 , 314 between each measurement area 304 , 306 , 308 , and 310 are between about 200 nm and about 2000 nm. For example, the spacing distances 312 , 314 between each measurement area 304 , 306 , 308 , and 310 are between about 500 nm and about 1500 nm, such as between about 750 nm and about 1250 nm. In some embodiments, each measurement region 304 , 306 , 308 , and 310 is considered a region of interest. In the embodiment illustrated in FIG. 3 , measurement areas 304 , 306 , 308 , and 310 are measurement boxes, which have two sets of parallel lines forming a closed parallelogram.

[0036] Another measure utilized is the inner region length 318 . The inner region length 318 is the distance from the coordinates 320 , 330 , 340 , and 350 to the edge of the measurement regions 304 , 306 , 308 , and 310 perpendicular to the line feature 302 . For example, the inner region length 318 is the distance from the primary coordinates 320 to the edge of the first measurement region 304 perpendicular to the line feature 302 . This inner region length 318 may be measured from either of two sides perpendicular to the line feature 302 . The inner region length 318 will be the same, measured from either edge of the first measurement region 304 , since the primary coordinates 320 are at the center of the measurement region 304 . When the edges are perpendicular to the line feature 302 , the distance from one edge of the first measurement area 304 to the opposite edge of the measurement area 304 is twice the inner area length 318 . The same approach can be taken to measure the inner region length 318 within any other of the other measurement regions 306 , 308 , 310 . In some embodiments, inner region length 318 is the same for all measurement regions 304 , 306 , 308 , 310 and coordinates 320 , 330 , 340 , 350 .

[0037] The inner region length and spacing distances 312 and 314 may be added together in different combinations to represent the total distance between one coordinate point and another. In one embodiment, the total distance between the primary coordinates 320 and the secondary coordinates 330 is the first interval distance 312 summed with twice the inner region length 318 . The total distance between the secondary coordinates 330 and tertiary coordinates 340 is the second interval distance 314 summed with twice the inner region length 318 . This relationship is the same for all subsequent distances between the coordinate points.

[0038] In some embodiments, the total distance between adjacent coordinate points of each set is the same. The total distance between adjacent coordinate points of each set may be automatically determined or preset by a controller programmed to determine the measurement distance. In each example, there may be a preset distance for the inner region length 318 . In some embodiments, the inner region length 318 is preset and the spacing distances 312 and 314 vary. Interval distances 312 and 314 may vary automatically to reduce noise, or may have a preset variation pattern. In some embodiments, the spacing distance 312 and 314 between each measurement area is varied to optimize the location of the measurements relative to the entire line feature 302 . Accordingly, measurements may be made within a certain range for the line feature 302 . For example, measurements may be undesirable near the edges of the line feature 302 . A user may wish to take data at a set distance from the edge of each set of line features 302 .

[0039] In some embodiments, the total distance between a set of adjacent coordinates is between about 200 nm and about 2000 nm. For example, from about 500 nm to about 1500 nm, such as from about 750 nm to about 1250 nm. In some embodiments, the total distance between a set of adjacent points is approximately 1000 nm.

[0040] A variable distance 316 may also be determined. The variable distance 316 is the distance from the reference axis to the line feature 302 at any given point along the line feature 302 . In some embodiments, the variable distance 316 is described as points in the x-coordinate along the line feature 302 . The reference axis is any axis that is in the same plane as the line feature 302 and parallel to the line feature 302 . In some embodiments, the reference axis is the edge of the field of view 300 parallel to the line feature 302 . In another embodiment, the reference axis may be any axis parallel to the line feature 302 as long as the same axis is used when measuring all points along the section of the line feature 302 . In some embodiments, the same reference axis as another section of line features 302 may be used for one section of line features 302 . In this embodiment, the reference axis for section S1 in FIG. 2 will be the same reference axis for section S2 in FIG. 2 . In some embodiments, the reference axis may be a reference axis for section S1 that is different from the reference axis used for section S2 . However, both reference axes are parallel to each other.

[0041] A variable distance 316 is found for each coordinate point along the line feature 302 , such that a first variable distance is found between the reference axis and the primary coordinates, and a second variable distance is found between the reference axis and 2 is found between the primary coordinates, a third variable distance is found between the reference axis and the tertiary coordinates, and an nth variable distance is found between the reference axis and the nth coordinate.

[0042] As shown in FIG. 3 , line features 302 are 2D line features 360 . The 2D line features 360 may be rotating elongate pillars, circular pillars, via hole features, or any other suitable 2D pattern. In this embodiment, the line feature 302 shown in FIG. 3 is the central axis of the 2D line feature 360 . Although 2D line features 360 are shown as rectangles in FIG. 3 , it is generally understood that 2D line features 360 are any two-dimensional shape. Two-dimensional shapes include rotating elongate pillars, circular pillars, and via hole features. In embodiments where the line features 302 are 2D line features 360 and the measured line features 302 are central axes of the 2D line features, the central axis is at the length 370 of the 2D line feature 360 . parallel The length 370 of the 2D line feature 360 is further defined as the long edge of the 2D line feature 360 .

[0043] 4 illustrates a schematic diagram of an interface boundary between two adjacent line features 302 , according to an embodiment of the present disclosure. Interface boundary 400 includes two adjacent sets of line features 302 , and an interface point 410 between two adjacent sets of line features 302 . The two adjacent sets of line features 302 may be similar to the first set of line features 204 and the second set of line features 206 of FIG. 2 . Similar to FIG. 2 , the first and second sets of line features 204 and 206 are grouped into sections 1 ( S1 ) and 2 ( S2 ) as shown in FIG. 2 .

[0044] The exemplary interface boundary 400 has a first section having a first section length 406 and a second section having a second section length 408 . The first section length 406 and the second section length 408 are the second of the same set of line features 302 from one interface point on the first end 420 of the set of line features 302 . Similar to or equal to the distance to another interface point (not shown) on the other end 422 . Interface point 410 is the point where two adjacent sets of line features 302 meet. Each set of line features 302 has a set of measured points 402 and 404 . Section S1 includes measured points 402 and section S2 includes measured points 404 . The measured points 402 and 404 are any of the primary coordinates 320 , the secondary coordinates 330 , the tertiary coordinates 340 , and the nth coordinates 350 , as well as points in between. Each of the measured points 402 and 404 has a reference arrow set 416 and 418 shown in FIG. 4 to show where each of the measured points 402 and 404 is on the horizontal axis. A first set of reference arrows 416 is shown in section S1 , while a second set of reference arrows 418 is shown in section S2 . Reference arrows 416 and 418 are oriented perpendicular to line features 302 .

[0045] By measuring the distance between the interface point 410 and a first point of the first set of measurement points 402 , a first edge distance 412 is calculated. The first point of the first set of measurement points 402 may be defined as a point closest to the interface point 410 of the first set of measurement points 402 . By measuring the distance between the interface point 410 and the first point of the second set of measurement points 404 , the second edge distance 414 is calculated. The first point of the second set of measurement points 404 may be defined as the point closest to the interface point 410 of the second set of measurement points 404 . This can be more readily confirmed by looking at the interface point 410 and reference arrow sets 416 and 418 . The first intersection point between the measurement points 402 , 404 and the reference arrow sets 416 , 418 may be measured as first and second edge distances 412 , 414 .

[0046] The first edge distance 412 and the second edge distance 414 may range from about 100 nm to about 500 nm, such as from about 200 nm to about 400 nm. In one embodiment, either the first edge distance 412 or the second edge distance 414 is about 350 nm. Measurements are generally not made within the first edge distance 412 from the interface point 410 or the second edge distance 414 from the interface point 410 . This is because points within this range of the interface boundary 400 contain a large amount of noise and variance. Such noise can dramatically skew the data collected from measurement points 402 and 404 . The first edge distance 412 and the second edge distance 414 are selected to reduce noise while still maintaining an accurate measurement.

[0047] It is noted that while 18 measurement points 402, 404 are shown in FIG. 4, other numbers of measurement points 402, 404 may be utilized. The minimum number of measurement points 402 , 404 that can be used is two measurement points 402 , 404 . The number of measuring points 402 , 404 is from about 2 measuring points 402 , 404 to about 50 measuring points 402 , 404 . The number of measurement points 402 , 404 may be generally described as a plurality of measurement points 402 , 404 . In one example, the number of measurement points 402 , 404 is increased to obtain a larger amount of data.

[0048] 5 illustrates operations of a method 500 for determining a line angle of a grating line, according to an embodiment of the present disclosure. Act 510 includes utilizing a measurement tool to track line features. The measurement tool may be a scanning electron microscope. The line feature may be a grating 112 as described above and shown in FIGS. 1 and 2 . A line feature may also be a set of line features 204 and 206 . In this embodiment, multiple line features can be tracked at any given moment. The line feature may also be the line feature 302 described above and in FIGS. 3 and 4 .

[0049] At operation 520 , a distance between each region of interest is established. In this embodiment, the regions of interest are the measurement regions 304 , 306 , 308 , and 310 discussed with reference to FIG. 3 . The distance between the respective regions of interest may be either the first spacing distance 312 or the second spacing distance 314 . A set distance between each region of interest is predetermined so that a sufficient amount of measurements are made to ensure accurate measurement results.

In operation 530 , C _x and C _y values are found along the line feature. The C _x and C _y values are equal to or substantially equal to the x-coordinates and y-coordinates of the respective coordinate point. This includes primary coordinates, secondary coordinates, tertiary coordinates, and n-th coordinates such that at least three or more coordinate points are measured. C _x and C _y values can be found for any xy axis, as long as the axes are used consistently across all coordinate measurements for that line feature.

[0051] In operation 540 , the slope and line angle of the line feature are found using the set of coordinate points found in operation 530 . A set of coordinate points is used to graph a theoretical line feature in a computer or controller. The slope of the theoretical line feature is calculated using a mathematical formula or program within a computer or controller device. In some embodiments, the slope of multiple line features in a single section is calculated after graphing the multiple theoretical line features. Once the slopes of the multiple theoretical line features are calculated, the average of the slopes of the multiple theoretical line features is calculated to produce an average theoretical line feature slope.

[0052] The line angle of each theoretical line feature can also be calculated using the slope. The line angle of each theoretical line feature is calculated using mathematical formulas and programs in a computer or controller.

[0053] As mentioned above, it is possible to utilize measurements from a single line feature, or a group of line features. One advantage of utilizing measurements from a single line feature is that measurements from a single line feature are more efficient and utilize less processing power to complete the measurements. One advantage of utilizing measurements from a group of line features is that the measurements can be averaged, which can provide more accurate and reliable measurements.

[0054] 6 illustrates operations of a method 600 for determining a stitch process quality of a grid structure, according to an embodiment of the present disclosure. Operation 610 includes determining line angles for two distinct line features, and operation 620 calculates the difference in line angle between the first line feature and the second line feature to find the line angle rotation. calculating, operation 630 includes comparing the line angle rotation to a design specification, and operation 640 includes determining a stitching process quality.

[0055] At operation 610 , line angles for a number of line features are calculated. The line angle calculation includes not only finding the line angle for two line features, but also finding the line angle for a plurality of additional line features when taking the average line feature slope within a section. The line angles are determined using the method described in method 500 . Act 610 differs from method 500 in that slope and line angles for lines in multiple adjacent sections are measured and calculated. The steps described in method 500 must be completed a second time for a second set of three or more coordinates found from a second line feature of line features of a separate but adjacent section.

[0056] In operation 620 , a difference between the first line angle of the line features of the first section and the second line angle of the line features of the second section is calculated. At operation 620 , the difference is taken by subtracting one of the first line angle or the second line angle from the other. The result of the difference between the first line angle and the second line angle is defined as the line angle rotation.

[0057] In operation 630, the line angle rotation found in operation 620 is compared to a design specification. The design specification may be the maximum line angle rotation allowed in the grating. In some embodiments, the design dimension may be less than or equal to 1/100 of a degree, such as less than or equal to 1/250, less than or equal to 1/500, or less than or equal to 1/1000 of a degree. By determining whether the calculated line angle rotation is less than, greater than, or approximately equal to the design specification, the line angle rotation and the design specification are compared.

[0058] At operation 640 , a quality of the stitching process is determined. The degree of line angle rotation compared to the design specification determines the stitching process quality. The stitching process quality may be determined on any designated scale. In some embodiments, the stitching process quality may be a pass or fail determination, such that if the line angle rotation is less than a design specification, the stitching process quality is considered sufficient to pass. . If the line angle rotation is greater than the design specification, the stitching process quality is considered to be rejected. Act 640 may be completed computationally on a computer and displayed on a digital interface, or may be completed by manually reviewing whether the stitching process is within desired design specifications. Other methods of determining stitching process quality are also contemplated, such as grading the stitching process quality on a scale of 1-100% or 1-10.

[0059] It is generally understood that, in certain embodiments, the line features referenced in the description above may be two-dimensional line features. For example, line features 204 , 206 , 302 , and 360 may be 2D line features.

[0060] While the foregoing relates to embodiments of the present disclosure, other and additional embodiments of the disclosure may be devised without departing from the basic scope of the disclosure, the scope of which is set forth in the following claims. is determined by

Claims (20)

A method of measuring a line angle comprising:
selecting a field of view of the grid structure;
identifying line features using a measurement tool;
selecting a starting point along the line feature;
measuring a primary coordinate, wherein the primary coordinate comprises a first x-coordinate and a first y-coordinate, wherein the first x-coordinate is a first distance from an edge of the field of view to the primary coordinate —;
measuring coordinates of at least secondary coordinates along the line feature, wherein the secondary coordinates include a second x-coordinate and a second y-coordinate, the second x-coordinate being the second coordinate from the edge of the field of view. is the second distance to the car coordinates -;
estimating a theoretical line feature using the primary coordinates and the secondary coordinates; and
calculating a line angle measurement between the theoretical line feature and a reference axis;
How to measure line angle. The method of claim 1,
wherein the measuring tool is a scanning electron microscope;
How to measure line angle. The method of claim 1,
wherein the line features are lines of a lattice structure;
How to measure line angle. The method of claim 1,
wherein the line feature comprises a two-dimensional line feature, and the two-dimensional line feature comprises one or more of an elongated pillar, a circular pillar, or contact holes.
How to measure line angle. 5. The method of claim 4,
wherein the first distance is a predetermined distance in a range from about 100 nm to about 500 nm;
How to measure line angle. The method of claim 1,
the starting point is greater than 150 nm from the first edge of the field of view, and the first edge of the field of view intersects the line feature;
How to measure line angle. The method of claim 1,
wherein the theoretical line feature is calculated using three or more coordinate points;
How to measure line angle. 8. The method of claim 7,
wherein the three or more coordinate points are separated by a predetermined distance,
How to measure line angle. 9. The method of claim 8,
wherein the predetermined distance varies between adjacent points of each pair;
How to measure line angle. A method of measuring line angle rotation of a lithographic grating structure, comprising:
Measuring a first line angle - Measuring the first line angle comprises:
(a) selecting a field of view of the grid structure;
(b) identifying line features using a measurement tool;
(c) selecting a starting point along the line feature;
(d) measuring the primary coordinates;
(e) measuring coordinates of at least quadratic coordinates along the line feature;
(f) estimating a theoretical line feature using the first and second coordinates; and
(g) calculating a line angle measurement between the theoretical line feature and a reference axis;
the primary coordinate comprises a first x-coordinate and a first y-coordinate, wherein the first x-coordinate is a first distance from an edge of the field of view to the primary coordinate;
the secondary coordinate comprises a second x-coordinate and a second y-coordinate, the second x-coordinate being a second distance from the edge of the field of view to the secondary coordinate;
measuring a second line angle, wherein measuring the second line angle comprises operation (a)-operation (g);
calculating a difference between the first line angle and the second line angle to determine the line angle rotation; and
comparing the line angle rotation to a design specification line angle measurement;
A method of measuring the line angle rotation of a lithographic grating structure. 11. The method of claim 10,
wherein the measuring tool is a scanning electron microscope;
A method of measuring the line angle rotation of a lithographic grating structure. 11. The method of claim 10,
wherein the line features are lines of a lattice structure;
A method of measuring the line angle rotation of a lithographic grating structure. 11. The method of claim 10,
wherein the line feature comprises a two-dimensional line feature, and the two-dimensional line feature comprises one or more of an elongate pillar, a circular pillar, or contact holes.
A method of measuring the line angle rotation of a lithographic grating structure. 11. The method of claim 10,
wherein the first distance is a predetermined distance in a range from about 100 nm to about 500 nm;
A method of measuring the line angle rotation of a lithographic grating structure. 11. The method of claim 10,
the starting point is greater than 150 nm from the first edge of the field of view, and the first edge of the field of view intersects the line feature;
A method of measuring the line angle rotation of a lithographic grating structure. 11. The method of claim 10,
wherein the theoretical line feature is calculated using three or more coordinate points;
A method of measuring the line angle rotation of a lithographic grating structure. 17. The method of claim 16,
wherein the three or more coordinate points are separated by a predetermined distance,
A method of measuring the line angle rotation of a lithographic grating structure. 18. The method of claim 17,
wherein the predetermined distance varies between adjacent points of each pair;
A method of measuring the line angle rotation of a lithographic grating structure. 11. The method of claim 10,
wherein the design specification line angle measurement is less than or equal to about 1/500 degrees;
A method of measuring the line angle rotation of a lithographic grating structure. A method of measuring line angle rotation of a lithographic grating structure, comprising:
positioning the measurement tool to measure the first image exposure in the grating structure;
Measuring a first line angle - Measuring the first line angle comprises:
(a) selecting a field of view of the grid structure;
(b) identifying line features using the measurement tool;
(c) selecting a starting point along the line feature;
(d) measuring the primary coordinates;
(e) measuring coordinates of at least quadratic coordinates along the line feature;
(f) estimating a theoretical line feature using the first and second coordinates; and
(g) calculating a line angle measurement between the theoretical line feature and a reference axis;
the primary coordinate comprises a first x-coordinate and a first y-coordinate, wherein the first x-coordinate is a first distance from an edge of the field of view to the primary coordinate;
the secondary coordinate comprises a second x-coordinate and a second y-coordinate, the second x-coordinate being a second distance from the edge of the field of view to the secondary coordinate;
positioning the measurement tool to measure a second image exposure in the grating structure;
measuring a second line angle, wherein measuring the second line angle comprises operation (a)-operation (g);
calculating a difference between the first line angle and the second line angle to determine the line angle rotation;
comparing the line angle rotation to a design specification line angle measurement; and
determining a stitch quality from a difference between the first line angle and the second line angle;
A method of measuring the line angle rotation of a lithographic grating structure.

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